When forming conventional copper structures in a via opening exposing an underlying relatively wide copper line, i.e. greater than about 2 μm, a bulge or hump of the underlying copper forms in the via due to the thermal process. The thermal process causes the copper to “grow” due to the thermal expansion of the underlying copper line at temperatures of from about 120 to 250° C.
A barrier layer is then formed within the via opening, lining the via opening and a second layer of copper is deposited over the barrier layer, filling the via opening. The second copper layer is then planarized to form a planarized copper structure. Later, during burn-in or reliability testing, the underlying copper layer hump shrinks due to stress migration (SM) leaving a void at the via bottom adjacent the barrier layer which deleteriously affects performance of the device(s).
U.S. Pat. No. 6,214,731 B1 to Nogami et al. describes a method of forming copper interconnection patterns whereby a barrier layer liner is formed within a via opening; a thin silicon layer is formed over the barrier layer liner; copper is deposited to fill the opening and is reacted with the thin silicon layer to form a thin layer of copper silicide at the interface between the copper layer and the barrier layer liner.
U.S. Pat. No. 6,211,084 B1 to Ngo et al. describes a copper silicide cap layer.
U.S. Pat. No. 6,046,108 to Liu et al. describes a selective copper silicide process and a copper interconnect process.
U.S. Pat. No. 5,447,887 to Filipiak et al. describes a copper silicide process.